Crystal presses are used to press plastic or glass crystals into the bezels of watches, including wristwatches. They are also used by watchmakers and most jewelry stores to press on the backs of watches after installing a battery and/or cleaning the watch.
All watchmakers have crystal presses. They've been around since the use of plastic crystals began. Plastic crystals, which are rarely used now, and glass crystals, which are used more today, can be put in with the same press by changing the different dies to fit a variety of cases.
The backs of watches are secured three ways: by screw-on, with screws around the edge, or by snap-on. The typical crystal press is used more today by jewelry stores to press on the backs after opening the case in order to perform a function such as changing the battery, and cleaning or repairing the watch. Since most presses are crystal presses, they allow the watch to be put into the press, dial side up, and the band to go under the press out of the way. After you change a battery, you must close the back of the case. If you cannot do it by hand, a press must be used. The watch must be put into the press dial side down with the back facing up. This is done in order to see that the back of the watch has been aligned with the back of the watch case so no damage is done when pressure is applied by the press.
When the watch is placed dial side down in the crystal presses used today, there is no place for the watch band to go. It will hit the top part of the press and not allow the watch case to be put flat into the press. If the band is flexible, there is no problem. However, if it is a band that cannot—be bent side to side, it will have to be removed from the watch. Some watch bands have spring bars which can get lost when removed and then need to be replaced; but more and more watches have pins that are pressed in. These pins have to be driven out with a punch and hammer and then be driven back in after the back has been pressed on.